[llvm-objcopy] Add file names to error messages

Summary:
This patch adds the file names to llvm-objcopy error messages. It makes easy to identify which file causes an error.

Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=41798

Reviewers: espindola, alexshap, rupprecht, jhenderson, jakehehrlich

Reviewed By: rupprecht, jhenderson, jakehehrlich

Subscribers: emaste, arichardson, jakehehrlich, MaskRay, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61993

llvm-svn: 361450